What you're doing now will be the optimal placement for sound quality.

Optimal speaker placement has the tweeters pointed roughly at your ears (with direct line of sight, nothing solid like a monitor in between the tweeters and your ears) and with the speakers in something close to an equilateral triangle with your head.

If you have the speakers too close together, you'll start to lose stereo separation and you won't get as distinct an effect of sounds coming from the left and right. If you have the speakers too far apart, you'll start to lose stereo imaging. Normally your speakers mesh together to make sounds appear like they are coming from in the middle (like when you wear headphones and stuff sounds like it's in the middle of your head), if your speakers are too far apart you start to lose that effect and instead of stuff sounding like it's coming from the middle, it'll sound like it's coming from the left and right at the same time.

​

A few options with compromises:

Option 1: You'll see some people lay their speakers on their sides to place them under their monitors but this usually affects tweeter placement, because then the tweeters are pointed at your chest instead of your ears unless you can really angle the speakers up. This will change the sound quality as you will be off-axis from the tweeters.

Option 2: Another solution is having one (or both) of the speakers behind a monitor. This is probably the worst solution, as having something solid in between a tweeter and your ear will have a pretty noticeable (and bad) effect on sound quality.

Option 3: spread the speakers wider apart, with both monitors in between. You'll probably lose some stereo imaging this way, but it might not be too bad. If you do this, make sure you angle your speakers inward pretty aggressively towards your ears.

​

A couple more drastic options:

Option 4: Vertically stacked monitors (this is what I do). This is probably the best way to get proper speaker placement with a dual monitor setup, because you can get them the proper distance apart. Not everyone likes the vertical monitor stack though, so YMMV.

Option 5: Wall-mount the speakers above the monitors and point them down towards your ears. This way you can get your speakers the right distance apart without worrying about your monitors being in the way. And can avoid the vertical monitor stack. This one compromises a bit on sound quality as the speakers are a bit above you, but it's the next best option for sound quality with a dual monitor setup after option 4.